Collet for fixing the inner end of a balance-spring of a timepiece



Feb. 22, 1966 ARQU HAL 3,236,041

GOLLET FOR FIXING THE INNER END OF A BALANCE-SPRING OF A TIMEPIECE FiledDec 2, 1964 United States Patent 3,236,041 COLLET FOR FIXING THE INNEREND OF A BALANCE-SPRING OF A TIMEPIECE Arnde Marquis, Mervelier, Bern,and Arnold Charpilloz, Bevilard, Bern, Switzerland; said Marquisassignor to said Charpilloz Filed Dec. 2, 1964, Ser. No. 415,275 Claimspriority, application Switzerland, Dec. 17, 1963, 15,341/ 63 6 Claims.(Cl. 58-115) The present invention relates to a collet for fixing theinner end of a balance-spring of a timepiece. This collet ischaracterized in that it comprises a cup and radially split ring,engaged in said cup, the cup having, from its bottom provided with acentral hole, bores of increasing diameter and, in its side wall, atleast a cut-out part extending over a portion of its height, the ringand the cup being arranged so as to form therebetween an annular chamberreceiving a portion of the balance-spring, the inner bent end of whichis hooked in the split of the ring, the ring having in addition adiametral groove in one of its faces, the diameters of said bores beingsuch that the ring, when it is partially introduced into the cup, may beturned with an easy fit in the cup and that, when it is completelypushed, it is firmly held in position in the cup, while it may still beturned in order to adjust the active length of the balance-spring andthe position of its point of attachment.

The accompanying drawing shows, by way of example, two embodiments ofthe invention.

FIGURE 1 is a diametral cross-sectional view of the first embodimentalong the line II of FIGURE 2.

FIGURE 2 is a top plan view of same.

FIGURE 3 is a cross-sectional view of the second embodiment along theline III-III of FIGURE 4.

FIGURE 4 is a top plan view of same.

In the first embodiment (FIGS. 1 and 2), the reference numeral 1 denotesthe outer cup of the collet. The cup 1 includes a bottom 2 provided witha central hole 3 and has three coaxial bores 4, 5 and 6 of increasingdiameter. The bore 4 has the shape of a circular groove which leaves arib 7 between itself and the hole 3 of the bottom 2. The bores 4, 5 and6 are interconnected by surfaces inclined at 45.

Two grooves 8 extending along secants which are symmetrical and makebetween each other an acute angle, are provided in the wall 9 of thecup 1. These grooves 8 are partially cut by the bores 5 and 6 of largerdiameter. Instead of the two grooves 8, it would also be possible toprovide a single wider groove, disposed only on one side of the cup 1.

The collet includes in addition an inner ring 10 adapted to cooperatewith the cup 1. The ring 10 consists of a cylindrical body provided atits ends with two collars 11 and 12 and has in its centre a hole 13. Thebottom corresponding to the collar 11 has a circular recess 14 the depthof which is slightly greater than the height of the rib 7 of the cup 1,the diameter of the recess 14 being slightly greater than the outerdiameter of said rib 7. The outer diameters of the collars 11 and 12 arechosen in such a manner that the ring 10 may be inserted with an easyfit into the upper portion of the cup 1, the collar 11 being in contactwith the intermediate bore 5 of the cup 1. The collars 11 and 12 have attheir lower portion bevelled edges inclined at 45 corresponding to theabovementioned surfaces inclined at 45 interconnecting the bores 4, 5and 6 of the cup 1.

The ring 10 is radially split as at 15, the split being somewhat widerthan the thickness of the balance-spring used. The ring 10 has inaddition a diametral groove 16 provided in its top surface, said groovebeing adapted to receive a tool for turning the ring 10 within thecup 1. The space lying between the collars 11 and 12 forms a groovewhich defines, with the wall 9 of the cup 1, an annular chamber 17adapted to receive the inner portion of the balance-spring 18, asexplained later.

The fixing of the inner end of the balance-spring 18 to the collet asshown and described is made as follows:

The split ring 10 is partially introduced into the top portion of thecup 1, With the collar 11 engaging the bore 5, so that the split 15faces one of the grooves 8. The choice of either of the grooves 8 willdepend on the direction of Winding of the balance-spring 18. Then, thebent end of the balance-spring 18 is placed in the split 15 and thegroove 8 so that the balance-spring 18 is at the level of the groovelying between the collars 11 and 12. Thereafter, by means of a suitabletool introduced into the groove 16, the ring 10 is turned in the Windingdirection of the balance-spring 18, i.e. in the counterclockwisedirection in FIG. 2, up to the position illustrated in FIG. 2, forinstance, which corresponds to a rotation of about Then, the ring 10 ispushed completely into the cup 1, so that the collar 11 enters the bore4 of the cup 1 and the collar 12 enters the bore 5; the diameters of thebores 4 and 5 are slightly smaller than the diameters of thecorresponding collars, so that the ring 10 is radially contracted and isfirmly held in position in the cup 1. However, the ring 10 may still beturned by means of the above-mentioned tool. At this moment, thefrequency of the oscillations of the sprung balance is compared withthat of the oscillations of a calibrated reference sprung balance. Ifnecessary, the ring 10 is turned in the one or the other direction,which permits to adjust, on the one hand,the active length of thebalance-spring and, on the other hand, the position of its point ofattachment. The frequency of the oscillations is again checked until thesprung balance oscillates in synchronism with the reference sprungbalance.

It will immediately be seen the great advantage afforded by the colletas shown and described over the collets in use up to now. If, afterchecking the oscillations, the inner end of the balance-spring had to beshortened, for instance, it was necessary to detach from the collet thebent end of the balance-spring, to cut a portion of the balance-spring,to bend the new end of the balance-spring, to fix again thebalance-spring to the collet, and to thus proceed for each checkingoperation, which represented a long and tiresome work. If a too longportion of the balance-spring had been inadvertently cut, it was nolonger possible to correct this error and the entire operation had to bemade again with a new balance-spring.

The work of searching the correct point of attachment of thebalance-spring is greatly simplified with the collet described. It, oncalibrating, the point of attachment has been passed beyond, it suflicesto turn the ring 10 slightly backwards for effecting the correction.When the point of attachment has been determined, the outer end of thesplit 15 makes a certain angle with the ends of the grooves 8. Onmounting the balance-springs of a same series, it will suffice to turnthe ring 10 by the same angle in order that the point of attachment becorrect for each of the balance-springs.

The second embodiment, illustrated in FIGS. 3 and 4, is somewhatsimplified, but shows the same advantages as the first embodiment. Thecup 19 includes a bottom 20 provided with a central hole 21 and hasthree bores 22, 23 and 24 of increasing diameter.

A cut-out part 25, consisting of a milling, is provided in the wall 26of the cup 19. It is partially cut by the bores 23 and 24 of largerdiameter.

The collet includes in addition an inner ring 27, adapted to cooperatewith the cup 19. The ring 27 consists of a cylindrical body provided atits top end with a collar 28 and has in its centre a hole 29. The outerdiameter of the cylindrical body of the ring 27 is chosen in such amanner that the ring 27 may be introduced with an easy fit into theupper portion of the cup 19, said cylindrical body being in contact withthe intermediate bore 23 of the cup 19.

The ring 27 is radially split as at 30, the split being somewhat widerthan the thickness of the balance-spring used. The ring 27 has inaddition a diametral groove 31 provided in its top surface, said groovebeing adapted to receive a tool for turning the ring 27 within the cup19. The collar 28 defines, with the wall of the cylindrical body of thecup 27, a shoulder 32 of the cup 19 and the wall 26 of the cup 19, anannular chamber 33 adapted to receive the inner portion of thebalance-spring 34.

The fixing of the inner end of the balance-spring 34 to the colletdescribed is substantially the same as for the first embodiment. Thering 27 is partially introduced into the top portion of the cup 19, withthe cylindrical body of the ring 27 engaging the bore 23, so that thesplit 30 faces the cut-out part 25. Then, the bent end of thebalance-spring 34 is placed in the split 30 so that the balance-spring34 is situated below the collar 28. Thereafter, by means of a toolinserted into the groove 31, the ring 27 is turned in the windingdirection of the balancespring 34, i.e. in the counter-clockwisedirection in FIG. 4, up to the position illustrated in FIG. 4, forinstance. Then, the ring 27 is pushed completely into the cup 19, sothat the cylindrical body of the cup 27 enters the bore 22 of the cup 19and the collar 28 enters the bore 24; the diameters of the bores 22 and24 are slightly smaller than the diameters of the cylindrical body ofthe ring 27 and of the collar 28, respectively, so that the ring 27 isradially contracted and is firmly held in position in the cup 19.However, the ring 27 may still be turned by means of the above-mentionedtool. At this moment, the frequency of the oscillations of the sprungbalance is compared with that of the oscillations of a calibratedreference sprung balance. If necessary, the ring 27 is turned in the oneor the other direction, until synchronism is attained between theoscillations of the sprung balance and those of the reference sprungbalance.

While certain representative embodiments and details have been shown forthe purpose of illustrating the invention, it will be apparent to thoseskilled in the art that various changes and modifications may be madetherein without departing from the spirit or scope of the invention.

What we claim is:

1. A collet for fixing the inner end of a balance-spring of a timepiece,characterized in that it comprises a cup and a radially split ring,engaged in said cup, the cup having, from its bottom provided with acentral hole, bores of increasing diameter and, in its side wall, atleast a cut-out part extending over a portion of its height, the ringand the cup being arranged so as to form therebetween an annular chamberreceiving a portion of the balance-spring, the inner bent end of whichis hooked in the split of the ring, the ring having in addition adiametral groove in one of its faces, the diameters of said bores beingsuch that the ring, when it is partially introduced into the cup, may beturned with an easy fit in the cup and that, when it is completelypushed, it is firmly held in position in the cup, while it may still beturned in order to adjust the active length of the balance-spring andthe position of its point of attachment.

2. A collet as claimed in claim 1, characterized in that the split ringhas two end collars, the space lying between said collars forming agroove which defines, with the wall of the cup, an annular chamberadapted to receive the inner portion of the balance-spring.

3. A collet as claimed in claim 2, characterized in that the bottom ofthe cup has inwardly a rib surrounding its central hole, and that,facing it, the face of the ring has a recess in which is disposed withplay the said rib.

4. A collet as claimed in claim 2, characterized in that the bores ofthe cup are interconnected by surfaces inclined at 45 and the collarsare bevelled also at 45 5. A collet as claimed in claim 2, characterizedin that said cut-out part consists of a groove extending along a secant.

6. A collet as claimed in claim 1, characterized in that the split ringincludes a cylindrical body provided with a single end collar, saidcollar defining, with the wall of the said cylindrical body of the ring,a shoulder and the wall of the cup, an annular chamber adapted toreceive the inner portion of the balance-spring.

No references cited.

LEO SMILOW, Primary Examiner.

1. A COLLET FOR FIXING THE INNER END OF A BALANCE-SPRING OF A TIMEPIECE,CHARACTERIZED IN THAT IT COMPRISES A CUP AND A RADIALLY SPLIT RING,ENGAGED IN SAID CUP, THE CUP HAVING, FROM ITS BOTTOM PROVIDED WITH ACENTRAL HOLE, BORES OF INCREASING DIAMETER AND, IN ITS SIDE WALL, ATLEAST A CUT-OUT PART EXTENDING OVER A PORTION OF ITS HEIGHT, THE RINGAND THE CUP BEING ARRANGED SO AS TO FORM THEREBETWEEN AN ANNULAR CHAMBERRECEIVING A PORTION OF THE BALANCE-SPRING, THE INNER BENT END OF WHICHIS HOOKED IN THE SPLIT OF THE RING, THE RING HAVING IN ADDITION ADIAMETRAL GROOVE IN ONE OF ITS FACES, THE DIAMETERS OF SAID BORES BEINGSUCH THAT THE RING, WHEN IT IS PARTIALLY INTRODUCED INTO THE CUP, MAY BETURNED WITH AN EASY FIT IN THE CUP AND THAT, WHEN IT IS COMPLETELYPUSHED, IT S FIRMLY HELD IN POSITION IN THE CUP, WHILE IT MAY STILL BETURNED IN ORDER TO ADJUST THE ACTIVE LENGTH OF THE BALANCE-SPRING ANDTHE POSITION OF ITS POINT OF ATTACHMENT.